Combine chicken, cornstarch, salt, sugar, pepper, soy sauce and garlic. Toss gently. Cover and chill 20 minutes.
Drain pineapple, reserving juice in a 1 quart glass measure. Set pineapple chunks aside. Add water to juice to equal 1 cup. Add 1/4 cup sugar, 2 tb. cornstarch, vinegar & 1 tb. soy sauce to pineapple juice. Stir well. Set aside.
Coat a large nonaluminum skillet or wok with cooking spray. Place over medium-high heat until hot. Add chicken, stir fry 5 to 7 minutes. Add carrots and 1/4 cup water. Cover and cook 1 minute. Add reserved pineapple and cranberries. Stir fry 1 minute. Reduce heat to medium. Add reserved juice mixture. Bring to a boil, stirring until thickened. Stir in bell pepper. Serve over rice.